1. Field of the Invention
The present invention generally relates to antennas and, more particularly, to phased array antennas.
2. Description of the Related Art
Recent advancements in satellite communications technologies have placed increasing system performance requirements on the antenna systems. This is particularly true for the phased array antenna systems.
Phased array antennas are generally composed of an array of radiating elements coupled to a signal input source through a number of identical beamformer modules. The beamformer modules are connected to the antenna main signal source and to the antenna frame through a wave guide interface surface so as to form a parallel stack of beamformer modules on the wave guide interface surface. A certain number of modules are arranged in equidistant parallel stacks which are perpendicularly connected to each wave guide interface surface. By convention, each radiating element is connected to a top end of each beamformer module and thereby form a subarray of radiating elements.
In the foregoing configuration, when the subarrays are placed in a side-by-side fashion, the array of radiating elements forms the top end of the antenna. The radiating elements individually or in the form of subarrays provide a directed beam of electromagnetic signals such as radio frequency (RF) signals. Each module contains phase shifter circuitry having phase shifter elements to control the phase of the inputted signals. By shifting the phase of the inputted signals in each phase shift element, the direction of the antenna beam can be changed without needing to mechanically move the antenna. The number of phase shifter elements per array module determines the number of beams that an antenna can generate and thus the RF throughput of the antenna.
Due to the strict design constraints on the dimensions of the radiating elements and the modules of an antenna, it is necessary to match the planar area occupied by the upper edge of a subbarray of radiating elements with the area of a wave guide interface surface. In other words, the projection of the planar area occupied by the radiating elements onto the interface surface defines the area that a module of the radiating element is permitted to occupy. Since the radiating elements follow strict dimensional limitations, this situation limits the size of the beamformer modules and hence the number of phase shifter elements per module, which in turn limits the number of beams that can be generated using a single module.
One prior art solution to this problem may be demonstrated with FIGS. 1A and 1B which illustrate two prior art beamformer modules 10 and 12, each having six phase shifters 14. The phase shifters 14 are connected to signal source input lines 16 extending between input connectors 17 and the phase shifters 14. The output wiring 18 from the phase shifters 14 is connected to radiating elements 20 and 22 which are coupled to top ends of the modules 10 and 12 respectively. In a side-by-side configuration shown in FIG. 1A, the modules 10 and 12 with the radiating elements 20 and 22 are placed on top of a wave guide interface surface 24 shown in FIG. 1B. The interface surface 24 has eight rows 26 having twelve input connection slots 28 to receive input connectors 17 of the modules 10, 12. In this configuration, a first group 30 of slots 28 receives the module 10 and the second group 32 of slots 28 receives the module 12. The other slots 28 are filled in with a similar side-by-side placement method. However, due to the design constraints, the above mentioned disadvantages still remain with this prior art method, which can only provide a limited six beam input per beamformer module and 12 beam inputs per row on the interface surface 24.
As can be seen, there is a need for the formation of alternative beamformer configurations in phased array antenna systems that increases the number of beams and the RF efficiency of the antenna.
In one aspect of the present invention, a modular beamformer system for providing signals to at least two radiating elements of a phased array antenna comprises a first beamformer module and a second beamformer module. The first beamformer module is coupled to at least two radiating elements. The first beam former module comprises at least two groups of beamforming circuitry on a primary plane of the first beamformer module and at least one feeder line extending from each beamforming circuit. Each feeder line is coupled to one of the radiating elements to transmit an output of each beam forming circuit. The second beamformer module is also coupled to at least two radiating elements. The second beam former module comprises at least two groups of beamforming circuitry on a primary plane of the second beamformer module and at least one feeder line extending from each beamforming circuitry. Each feeder line is coupled to one of the radiating elements to transmit an output of each beam forming circuitry.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.